Low Frequency Oscillation Modes Estimation In Power Systems Using Adaptive-projection Intrinsically Transformed Multivariate Empirical Mode Decomposition

With the rapid development of Chinese economy,the requirements for electrical energy must be continuously increased,which has led to the continuous expansion of the size of the power grid,and the power system has been approaching its stable limit operation.The problem of low-frequency oscillations caused by weak damping of the system has become one of the important factors that threaten the safe and stable operation of the power grid.so quickly identifying the low-frequency oscillation mode of the power system,especially the weak damping mode and negative damping mode,is of great engineering significance to the security early warning of the power grid.This paper proposes a new method to estimate the low frequency oscillation modes from synchrophasor measurements in power system by using Adaptive-projection intrinsically transformed multivariate empirical mode decomposition(APIT-MEMD)and Hilbert-Hung transform(HHT).A multi-channel multivariate empirical mode decomposition(MEMO)is proposed to suppress the influences of mode mixing caused by empirical mode decomposition(EMD),and further enhance the computational efficiency of decomposing multiple measurements.The traditional MEMD to estimate the dominant oscillation modes from the measurements may fail caused by the inter-channel imbalances and correlations,and the mode mixing was still not effectively resolved.This paper proposes a new method to estimate the dominant oscillation modes from the measurements in power system by using APIT-MEMD.Firstly,the multi-channels measurements was decomposed by APIT-MEMD,and the intrinsic mode functions(IMF)signals with different oscillation mode scales in each measurement channel are accurately separated;and then the critical IMF associated with the dominant oscillation mode are determined by the Teager energy operator;The HHT was applied to identify the oscillation frequency and damping ratio of each dominant oscillation mode.The method was validated by 16-generator 68-bus test system and the PMU datas collected from the Liaoning Power Grid.The results validate that the proposed approach exhibit a highly accurate and efficient performance to estimate dominant oscillation modes from synchrophasor measurements.